1. Field of the Invention
The present invention relates to a transmission of a vehicle which includes a gear shift mechanism formed by arranging gear trains of a plurality of selectively establishable shift positions between a shift input shaft and a shift output shaft, a shift drum rotatably supported on an engine case for selectively establishing one of the plurality of gear trains in response to a rotational position, a shift spindle rotatably mounted on the engine case so as to be rotatable in response to a shift manipulation, a shift drive force transmitting mechanism arranged between the shift spindle and the shift drum so as to rotatably drive the shift drum in response to the rotation of the shift spindle, a lost motion means arranged in the shift drive force transmitting mechanism so as to temporarily accumulating a shift drive force transmitted from the shift spindle and a shift stopper mechanism resiliently holding a rotary position of the shift drum in a state where one of the plurality of gear trains is established or in a neutral state.
2. Description of Background Art
Japanese Patent No. JP-UM-A-01-116240 discloses a transmission for a vehicle wherein a lost motion means in a shift drive force transmitting mechanism is arranged between a shift spindle and a shift drum. Such a transmission can acquire a favorable operation feeling due to a lost motion action generated by a lost motion means when a dog contact arises at the time of changing over the establishment of a gear train in a gear shift mechanism.
In adopting the structure as disclosed in JP-UM-A-01-116240 which arranges the lost motion means in the shift drive force transmitting mechanism in a transmission which automatically changes over the engagement/disengagement of a clutch interposed between a power source output shaft and a shift input shaft using an actuator such as a power-operated motor, it is necessary to start a power transmission interrupting operation of the clutch at proper timing. More specifically, the lost motion means are not uniform in property. Thus, in performing a power transmission interrupting operation of the clutch in conformity with a shift manipulation, for example, when sufficient power is not accumulated in the lost motion means, a shift drum is not rotated until power for rotating the shift drum is accumulated in the lost motion means even when the clutch starts a power transmission interrupting operation, there exists a possibility that a shift manipulation which conforms to the shift operation is not performed. Further, when sufficient power is accumulated in the lost motion means, the shift drum is rotated before the power transmission interrupting operation of the clutch starts thus giving rise to a possibility that a shift operation which conforms to the shift manipulation is not performed.